Update rails to version 4.2

Furthermore it was necessary to add the following gems:
- responders
- web-console

And additional it was necessary to update these gems manually:
- devise
- turbolinks
- delayed_job_active_record
- money-rails

And the corresponding dependencies.
http://edgeguides.rubyonrails.org/upgrading_ruby_on_rails.html#upgrading-from-rails-4-1-to-rails-4-2

spec/models/ticket_spec.rb

@@ -68,11 +68,11 @@ describe Ticket do
              user: user,
              ticket: ticket,
              quantity: 20)
-      expect(ticket.total_price(user)).to eq(20 * 50)
+      expect(ticket.total_price(user)).to eq(Money.new(20 * ticket.price_cents, 'USD'))
     end
 
     it 'returns zero if the user has not bought this ticket' do
-      expect(ticket.total_price(user)).to eq(0)
+      expect(ticket.total_price(user)).to eq(Money.new(0, 'USD'))
     end
   end
 
@@ -82,11 +82,11 @@ describe Ticket do
              user: user,
              ticket: ticket,
              quantity: 20)
-      expect(Ticket.total_price(conference, user)).to eq(20 * 50)
+      expect(Ticket.total_price(conference, user)).to eq(Money.new(20 * ticket.price_cents, 'USD'))
     end
 
     it 'returns zero if the user has not bought this ticket' do
-      expect(Ticket.total_price(conference, user)).to eq(0)
+      expect(Ticket.total_price(conference, user)).to eq(Money.new(0, 'USD'))
     end
   end
 end